Acoustic energy transmission device

ABSTRACT

An apparatus for transmitting energy in the form of acoustic energy from one location to another, the energy being supplied at one location to the transmitting apparatus from an acoustic electric energy source through an electromechanical transducer and supplied at the other location by the transmitting apparatus to an electrical load through a second electromechanical transducer.

United States Patent 1 Skinner et al.

[451 Dec. 4, 1973 ACOUSTIC ENERGY TRANSMISSION DEVICE [75] Inventors: Dale D. Skinner, Turtle Creek; John H. Thompson, Pittsburgh; Robert H. Whittaker, Export, all of Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: May 4, 1972 [21] Appl. No.: 250,395

[52] US. Cl 3l0/8.3, 259/1 R, 310/8.1, 3l0/8.7, 310/26, 333/30 R [51] Int. Cl I-I0lv 7/00 [58] Field of Search 3l0/8.1, 8.2, 8.3, 310/8.7, 9.1, 26; 333/30 R; 259/1 R; 317/58 [56] References Cited UNITED STATES PATENTS 12/1970 McMaster et al 333/30 R 3,584,327 6/1971 Murry 310/8.7 UX 3,166,840 1/1965 Bancroft et a1... 310/26 X 3,173,034 3/1965 Dickey et a1 3lO/8.7 X 3,140,859 7/1964 Scarpa 310/8.2 X 3,591,862 7/1971 Winston 3l0/8.3 X

Primary Examiner-J. D. Miller Assistant Examiner-Mark O. Budd Attorney-A. T. Stratton et al.

[5 7] ABSTRACT An apparatus for transmitting energy in the form of acoustic energy from one location to another, the energy being supplied at one location to the transmitting apparatus from an acoustic electric energy source through an electromechanical transducer and supplied at the other location by the transmitting apparatus to an electrical load through a second electromechanical transducer.

6 Claims, 11 Drawing Figures PATENTEBBEB 4W 3.777.189

SHEET-1 UF 4 F IG.I.

4 MATGHING I \TRANSFORMER voI.TAGE TRANsMITTER REGULATOR RECTIFIER RECEIVING TRA sDuGER\ l 6 I [LINE POTENTIAL l I {GROUND POTENTIAL I MATCHING 6 I TRANSFORMER 1 1 POWER 5 TRANSMITTING REGEIvER OSCILLATOR I2 iT6RANSDUCER I8) 44 L FEEDBACK FEEDBACK sENsING NETWORK Y 3 22 f 32\ I I II II |I l J INSULATING I 'IIZ \INsuLATING K WAVE GU'DE TAII. WASHER J WASHER HEAD FIG. 2

PATENTEU 41975 3.777. 189

SHEET 3 BF 4 35 L3 5 YPLASTIC =4 x I05 PSI :3 LOSS FACTOR=.O5 o O o 2 Y 7 0 GLASS=lxlO PS! m LOSS FACTOR =.oo5

g 2 LL] G FRACTION OF GLASS FIG.5.

1 ACOUSTIC ENERGY TRANSMISSION DEVICE CROSS-REFERENCED APPLICATIONS This application is an improvement over application, Ser. No. 127,874 filed Mar. 25, 1971 for Signal Transmitting System For Extra High Voltage Transmission Line, now US. Pat. No. 3,678,339 and assigned to the same assignee as is this application.

BRIEF SUMMARY OF THE INVENTION The general concept of the energization of a transmitter, associated with a transmission line operating at upwards of 500 Kv, with energy from a source operating at nearly earth potential whereby a signal indicating an operating condition of the line (current flow) may be transmitted to devices operating at substantially ground potential is described and claimed in said copending application.

In certain other prior art devices, transmitters of this type were energized with energy derived from the transmission line. In some instances energy storage devices charged by this derived energy were provided to energize the transmitter during periods when the transmission line was deenergized. The energy storage devices while an improvement over the direct energy deriving devices left much to be desired because of the life expectancy of the storage devices and the difficulty of their replacement. Also there was a limit to energy which could be stored and to the time periods that the storage device could maintain the transmitter in operating condition with the transmission line deenergized.

With present day line voltages it is essential for the proper protection thereof to deenergize a faulted line section in the matter of a few milliseconds. This is just as true when a line fault occurs when the line is energized as it is when an attempt is made to energize a faulted deenergized line. The said copending application, Ser. No. 127,874 discloses and claims a protecting device which is relatively secure in that it contains no storage device operating at high potentials which cannot be easily serviced and only a bare minimum of apparatus which is not easily accessible. This invention is concerned with providing a more efficient apparatus for supplying operating energy to the transmitter.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be had to the preferred embodiment, exemplary of the invention, shown in the accompanying drawings in which drawings:

FIG. I is an abbreviated view of a power supplying apparatus for delivering power from a potential supply which is substantially that of earth to an energy utilizing device operating at high potential with respect to earth potential and which embodies the invention;

FIG. 2 is an enlarged view of one end portion of a wave guide of FIG. 1 showing in greater detail the attachment of the piezoelectric transducer;

FIG. 3 is a view of a modified form of a wave guide embodying the invention;

FIG. 4 is an enlarged view of an end portion of a modified form of wave guide with a piezoelectric transducer attached;

FIG. 5 is a graph showing the relationship, at three different frequencies, between the percentage of glass vs the attenuation of the wave guide in DB/meter;

FIG. 6 is a view of a modified form of transducer for vibrating the wave guide;

FIG. 7 is a sectional view taken substantially along the line VII-VII of FIG. 6 looking in the direction of the arrows;

FIG. 8 is a partial view showing the electrical connections to the wafers used in the modified form of FIGS. 6 and 7;

FIG. 9 is a partial view of a further modified form of transducer for vibrating the wave guide;

FIG. 10 is a sectional view taken substantially along the line X-X of FIG. 9 looking in the direction of the arrows; and

FIG. 11 is a partial view showing the electrical connections to the wafers used in the modified form of FIGS. 9 and 10.

Referring to the drawings by characters of reference, the numeral 1 designates generally a transmission line conductor, the current in which, is monitored by a curent transformer 2 which modulates a transmitter 4. The transmitter 4 transmits a signal indicative of one or more characteristics of the current in line 1 to a receiver 6 at ground or earth potential. The details of the transmitter 4 and of the receiver 6 may take any desired form. A preformed foam is a type in which the output signal is transmitted as light through a light pipe diagrammatically illustrated by the dash line 8.

Power for energizing the transmitter 4 is derived from the power oscillator 10 the output of which is coupled to the input terminals 12, 14 and 14A of a transducer- 16 through a matching transformer 18. If desired, the operating frequency may be modulated by means of the feedback network 20 to provide a maximum power transmission to the elongated rod-like wave guide 22.

The structural details of the transducer 16 at end portions of the wave guide 22 are identical and one only thereof will be discussed in detail. As illustrated in FIG. 2, the transducer 16 comprises two annular piezoceramic wafers l9 and 19A having their end walls silvered and being longitudinally polarized. The adjacent silvered end walls are connected to the input terminal 12 while the outwardly facing silvered end walls are connected to the input terminals 14 and 14A. When a potential of one polarity is applied to the silvered surfaces of a wafer it tends to decrease in thickness. Conversely, when the potential is of opposite polarity the waver increases in thickness. The wafer 19 is assembled in opposite polarization to the wafer 19A so that when the input terminals are energized with an alternating potential both wafers increase and decrease in thickness together. A suitable material for the wafers l9 and 19A is lead zirconate titanate sold by Gulton Industries, Inc., Metuchen, New Jersey, designated by them as I-IDT-3l. This material is strong in compression but weak in tension and must therefore by prevented from exerting a tensile force.

The wafers l9 and 19A have first and second outer surfaces 24 and 26 clamped between the transducer head 28 and the transducer tail 33 by the nut 36 screwthreaded on a through bolt 30 and which compresses a belleville washer 31 against the outer end wall of the tail 33. The bolt 30 extends axially through the transducer 16 and is screwthreadedly secured to the end wall 29 of the head 28. The outer silvered end surfaces 24 and 26 of the wafers l9 and 19A are insulated from the head 28 and tail 33 by the insulating washers 34. When the wafers l9 and 19A are energized with an alternating potential the expansion and contraction thereof minutely vibrate the lower or transmitting end portion of the wave guide 22 (or at the top or receiving end portion are minutely vibrated by the guide 22).

The head member 28 is cup-shaped and receives the adjacent end portions of the wave guide 22 which is suitably secured therein with the end portion of the guide 22 adjacent its bottom end wall 29. The nut 36 threadedly carried by the bolt 30 stresses the resilient belleville washer 38 and resiliently clamps the wafers to the end wall 29. As stated, the washer 38 must exert sufficient resilient force to prevent the transducer 16 from exerting a tensile force.

The tail member 33 acts as 2 reaction mass for the transducer 16, giving it something to push against. The stress bolt 30 and belleville washer 38 have greater compliance than the transducer 16. Very little vibration energy exists on the stress bolt 30 beyond the tail nut 36. The tail member 33 should be massive with respect to the head member 28. A weight ratio of greater than 2 to l is desirable and should be at least equal to l to l.

The upper head member 28 couples the upper transducer 16 to the upper end portion of the wave guide 22. Preferably the guide 22 is suspended from its upper end by means of a nut 40 threaded on the end of the upper bolt which extends through an aperture in a supporting member 42. The lower bolt 30 may if desired loosely extend through a locating hole in a lower supporting member 44. With the guide so supported, it is held with its ends restrained but not clamped. It will be apparent its lower end may move vertically relative to the member 44 to permit expansion and contraction of the guide 22 due to temperature changes or otherwise.

The wave guide material, as will be discussed in detail below, should be inorganic electrically non-conducting of high density and have a low loss factor. A very suitable material is pyrex glass which has a'density of about 2,500 Kg/cubic meter or the more expensive quartz may be used. Such a material in long lengths is subject to breakage and is difficult to handle, however it may be usable under some conditions as for example when there is a straight vertical path between the supports 40 and 44 as illustrated in FIG. 1 and protected against being hit. r

Under many instances it is too difficult to provide a straight run or to insert a non-bendable rod into position or even to transport a solid glass or quartz rod to the location in which it is to be used. We have found that a wave guide manufactured from a plurality of thin threads of the same material suitably bonded together by a suitable epoxy such as Bis Phenol A is quite satisfactory. The presence of the epoxy markedly increases the loss in the guide so that the percentage of the high density fibers should be as large as possible. Further the guide should be as free of voids as possible since the presence of voids causes undesirable local hot spots. We have found that if after a cable of glass fibers has been impregnated with the epoxy it is stretched and twisted longitudinally a flexible guide containing as much as 85 percent fiber results. While such a rod fabricated of glass fiber has greater losses than a solid quartz or pyrex glass rod, the losses are not excessive. When the percentage of glass is reduced much below 40 percent the losses become so great that for practical purposes the rod cannot be used for the transmission of power in quantities sufficient to energize power consuming devices as distinguished from supplying control signals.

FIGS. 3 and 4 illustrate a form of the invention in which a plurality of smaller diameter rods 122 are coupled in parallel between two heads 128. This form as illustrated in FIG. 3 is more flexible than the single rod 22 illustrated in FIGS. 1 and '2 and may be coiled for its easy transporting and threading around any obstructions which would prevent a straight line run of rod. For example 12 rods of one-quarter inch diameter would have approximately the same total crosssectional area as a single rod of seven-eighths inch diameter and could be bent to a lesser radius.

FIG. 4 illustrates an assembly of four one-quarter inch rods in one dimension with three one-quarter inch rods in the second dimension secured to a transducer 16A which except for the head 128 is identical to the transducer 16. If great flexibility is desired for bending this rod in a single direction the twelve one-quarter inch rods could be in a row. This would, of course, decrease the flexibility for bending in the plane of the row and increase the flexibility in the plane perpendicular to the row. We have found that the acoustic energy can be transmitted along a flexed or curved rod or group of rods without substantially decreasing the power thereof below that of the straight run rod or rods.

Assuming a single rod of seven-eighths inch diameter or twelve rodsof one-quarter inch diameter composed of percent glass and 15 percent epoxy, a power source having a frequency of 20 kHz and a power output of 50 watts of simple harmonic motion, the driving force would be 8.15 pounds per square inch peak and the movement of the head member 28 or 128 as the case may be would be 2.4 X 10 inches peak. If the frequency of the power source is reduced to 10 kHz the movement or displacement would be increased to 4.8 X 10 inches peak with the same driving force of 8.15 pounds per square inch. For most practical installations the driving or source frequency should be somewhat above the frequency normally heard by persons or above 16 kHz. Therefore 20 kHz or more is a preferred frequency since no audible noise will be produced.

The values shown in FIG. 5 approximate those of a single seven-eighths inch diameter rod or of twelve one-quarter inch diameter rods at frequencies of 10, 20 and 30 kHz. It will be observed that at percentages of glass much below 40 percent the attenuation greatly increases. This not only affects the magnitude of the power input required for the same output power but the lost power appears as heat which tends to cause rapid deterioration of the rod and a short life thereof. We have found that following the techniques set forth above with twisted glass fibers a rod of upwards of 85 percent glass may be formed which is relatively insensitive to shattering and at the same time is flexible as described above. This percentage of glass has a DB/meter attenuation of about 0.5 at 20 kHz which is our preferred frequency and glass percentage. With this attenuation the rod may be enclosed in the housing which houses the breaker operating mechanism as illustrated in the said copending application.

The absolute power carrying capacity can be increased by increasing the rod area up to a diameter which approaches 0.3 times the wavelength of the acoustical energy. At diameters above this the propagation begins to deviate substantially from the longitudinal mode in that the Poissons contraction and expansion couples sideway motions into the main mode.

The choice of frequency depends upon the number of factors. If it is too low, the rod will not propagate a longitudinal mode because of the easily excited other modes such as flexure. If the rod is maintained in tension lower frequencies can be transmitted but the problems associated with the maintenance of the proper tension, even of a straight rod due, to temperature and other environmental conditions are troublesome and such frequencies are in the audible range and objectionable from that viewpoint. Also at the lower frequencies the flexing resonance at bends or curvatures of the rod tend to decrease the transmitted power and increase the losses which unduly heat these portions of the rod or rods.

The transducer 168 of FIGS. 6-8 have segmented wafers 1 19 and 119A each of which comprise four segments 119B, 119C, 119D and 119E. The segments are polarized longitudinally of the transducer 168 and are insulated from the head 128A and tail 133A by the annular insulating washers 134A and 1348 respectively. As shown in FIG. 6, the transducer has an annular section 135 intermediate the segmented wafer 119 and 119A and insulated therefrom by annular insulating washers 136A and 1368. A first annular insulating spool 137A has one end surface cemented to the head 128A and its other end surface cemented to the adjacent end surface of the section 135 by a high tensile epoxy such as epon 6. Similarly, a second annular in'sulating spool 1378 is cemented to the section 135 and tail 133A. A suitable material for the spools is polytetrafluoroethylene.

The segments have their longitudinally extending side walls covered with an electrically conducting material 120 such as silver and they are longitudinally polarized. The radially extending end walls unlike the wafers 19 and 19A are not covered with electrically conducting material. The segments 119C and 119E are polarized in a first longitudinal direction while the segments 1198 and 119D are polarized in the second or opposite longitudinal direction. The adjacent longitudinally-extending' side walls of the segments l19C-l 19D and 11915-1198 are electrically connected together by a conductor 121A which in turn is connected to a lead wire 122. Similarly the adjacent longitudinally extending side walls of the segments ll9B-l19C and 119D-l19E are electrically connected together by a conductor 123A which is in turn connected to a lead wire 124. The segments of the segmented wafer 119 are similarly connected to the conductors 122 and 124 by the conductors 121 and 123. The segments 1198 and 119D are polarized in one longitudinal direction while the segments 119C and 119E are polarized in the opposite longitudinal direction.

When an alternating potential is applied to the leads 122 and 124 the transducer will deliver a rotational vibration to its head 128A which is cemented to one end portion of the wave guide 122A which may be of the type shown in FIG. 2 or FIG. 4; the type shown in FIG. 2 being illustrated.

The transducer 16C, fragmentarily illustrated in FIGS. 9, and 11, comprises a head 128B cemented to one end portion of a wave guide 1228 and at least one segmented wafer 11% sandwiched between the tail 1333 and head 1288 and insulated therefrom by the insulating washers 134C and 136C.

The segmented wafer 119F comprises two segments 1196 and 1191-1. These segments are longitudinally polarized and their outer end walls are coated with an electrically conducting material such as silver 1208 as are the wafers 19 and 19A. The outer end walls of the segments 119G are energized at the opposite polarity to the segments 1191-1 as illustrated in FIG. 11 so that when the leads 1238 and 1248 are energized with an alternating potential one of the segments 119G and 1191-1 will tend to expand longitudinally and the other of the segments 1191-1 or 119G will tend to contrast longitudinally thereby giving a rocking vibratory motion to the wave guide 1228 for transmitting power therealong to the receiving transducer.

A spool 137C is positioned concentrically of the wafer 119F and has its opposite end walls cemented to the head 128B and the tail 133C. The spool 137C like the spools 137A and B are preferably of insulating resilient material such as polytetrafluoroethylene.

While only a single segmented wafer 119F is illustrated it will be apparent that a plurality thereof may be used. It will also be possible to reverse the polarization of the segments 1190 and 1191-1 and to energize the surface B thereof adjacent the washer 134C from the same lead 1238 or 1248 and the other surfaces 120B adjacent washer 136C from the other of the leads 1248 or 1238.

What is claimed and is desired to be secured by United States Letters Patent is as follows:

1. An acoustic energy transmission device comprising, first and second electro-acoustic transducers, each said transducer including an electrical circuit and a force exerting surface, an elongated substantially void free wave guide having first and second end portions, said guide comprising not less than 40% of inorganic electrically non-conducting low mass density fibers and a plastic binder bonding said fibers together, first means holding said surface of said first transducer to said first end portion and second means holding said surface of said second transducer to said second end portion.

2. The combination of claim 1 in which said fibers are not greater than 0.01 inch in diameter.

3. The combination of claim 2 in which said fibers extend parallel to each other and spiral along the axis of said guide.

4. The combination of claim 2 in which said guide comprises a plural number of separate groups of said fibers.

5. The combination of claim 4 in which said groups are spaced from each other to provide integral groups of said fibers.

6. The combination of claim 1 in which said holding means includes a supporting member secured tothe end portion of said guide with which it is associated, each saidholding means further including means supported by its said supporting member and resiliently holding the said surface of the associated said transducer against the associated said end portion of said guide. 

1. An acoustic energy transmission device comprising, first and second electro-acoustic transducers, each said transducer including an electrical circuit and a force exerting surface, an elongated substantially void free wave guide having first and second end portions, said guide comprising not less than 40% of inorganic electrically non-conducting low mass density fibers and a plastic binder bonding said fibers together, first means holding said surface of said first transducer to said first end portion and second means holding said surface of said second transducer to said second end portion.
 2. The combination of claim 1 in which said fibers are not greater than 0.01 inch in diameter.
 3. The combination of claim 2 in which said fibers extend parallel to each other and spiral along the axis of said guide.
 4. The combination of claim 2 in which said guide comprises a plural number of separate groups of said fibers.
 5. The combination of claim 4 in which said groups are spaced from each other to provide integral groups of said fibers.
 6. The combination of claim 1 in which said holding means includes a supporting member secured to the end portion of said guide with which it is associated, each said holding means further including means supported by its said supporting member and resiliently holding the said surface of the associated said transducer against the associated said end portion of said guide. 